1. Field of the Invention
The present invention relates to a blade-type cleaning device for transfer-type electrophotographic copying machines, and more particularly to a blade-type cleaning device comprising a blade member of elastic material which is placed in pressing contact with the surface of a photoconductive member to remove residual toner from the surface.
2. Description of the Prior Art
Blade-type cleaning devices heretofore known can be divided into two general groups, those in which, as shown in FIG. 1, of the two angles between the blade member 61 and line X.sub.1 tangent to the point of contact C.sub.1 between the blade member 61 and a photoconductive member 2 rotatable in the direction of the arrow a, the angle (hereinafter referred to as "contact angle") .theta..sub.1 on the uncleaned portion of the photoconductive member 2 moving toward the blade is an obtuse angle, and those in which as shown in FIG. 2, the contact angle .theta..sub.2 between the blade member 61 and the tangent X.sub.2 to the contact point C.sub.2 is an acute angle.
In the arrangement shown in FIG. 1 in which the blade member 61 presses against the surface of the photoconductive member 2 at an obtuse contact angle .theta..sub.1, the frictional force between the photoconductive surface and the blade member 61 tends to compress the blade member and deforms the blade member 61 transversely of the axis thereof, so that the contact point C.sub.1 is subjected to a very great force. When rotation of the photoconductive member 2 is initiated, an especially high frictional force acts, and there is a possibility that the photoconductive member will be damaged.
The blade member 61 of FIG. 2 is not subjected to a friction force which tends to compress it, so that the possibility of this type of damage is not present. The arrangement of FIG. 2 nevertheless is deficient as compared with that of FIG. 1 in that the cleaning force is smaller and the blade member is likely to leave some residual toner on the photoconductive member depending on the angular setting of the blade member 61.
Furthermore the blade member of the cleaning device of the types described is held in contact with the surface of the photoconductive member at a pressure sufficient to remove fine toner particles from the surface. The cleaning effect achieved depends largely on this pressure, the angle of contact between the blade member and the photoconductive member, etc. Thus the blade member must be set relative to the photoconductive member with high accuracy.
On the other hand, the photoconductive member of electrophotographic copying machines is generally detachable from the main body of the machine as a unit to permit replacement, but if the blade member is in pressing contact with the surface of the photoconductive member, it is very disadvantageous for detaching or installing the photoconductive member.
For example, when the photoconductive member is a drum-shaped member which is movable axially thereof for removal and installation, the blade member will mar the photoconductive surface when it is in pressing contact therewith. The photoconductive member requires a considerable force for installation if the blade member is set at a certain angle or will be improperly deflected by the pressure of the blade member.